We ride horses, donkeys, and mules. Zebras are closely related, so why have they never been successfully domesticated?
The answer is at once simple and complicated.
But I’ve Seen a Zebra Being Ridden
Individual zebras are sometimes trainable. However, the majority of zebras are actually too small to ride. This is of course exacerbated by the fact that they haven’t been selectively bred to be ridden. We’ve made our horses ridable.
Zebras are more useful for pulling carts. Lord Walter Rothschild drove a four in hand of zebras to Buckingham Palace.
So, yes, zebras can be trained. What they can’t be is domesticated.
Why Can’t Zebras Be Domesticated?
It boils down to a very simple and very complex difference between horses and asses (it’s an ass until it’s domesticated, then it becomes a donkey ;)) and zebras.
The tl;dr: Zebras aren’t asses, they’re assholes.
When Europeans colonized Africa they wanted to domesticate zebras because zebras, being a native species, were immune to trypanasomiasis, which is often fatal in horses. They didn’t ask themselves why the natives had never domesticated zebras.
Like donkeys, zebras lean towards fight as a defense not flight. And their main predator is the lion.
The main predator of the donkeys in the middle east was canids like the wolf. Donkeys can also be aggressive if not properly handled.
Zebras have killed lions. And people. Quite a few people; they’re statistically the most dangerous animal kept in zoos.
Horses kick out of reflex. Zebras kick with intent to kill.
They will kill each other, too. When you introduce a horse to a new herd, a bit of violence is not uncommon and we take steps to reduce it. They have to sort themselves out and work out where they fit in the herd, not so much in a hierarchical manner as in the complicated network of friendships horses form.